In a conventional power steering apparatus for vehicles, a control valve and the operation chambers of the power cylinder are connected by means of external pipes. Accordingly, there is a problem that the power steering apparatus is not easy to mount on a vehicle. Another problem is that the external pipes are sometimes damaged by sprung stones and the like. Furthermore, such piping requires an additional assembly operation, thereby decreasing productivity of the apparatus.
To overcome these problems, power steering apparatuses, in which supply/discharge flow paths for connecting the control valve with the operation chambers of the power cylinder are formed by casting, have been proposed as described in Unexamined Japanese Utility Model Publication No.Sho55-104577, Unexamined Japanese Patent Publication No. Hei7-257408, Unexamined Japanese Patent Publication No. Hei7-257409, and Unexamined Japanese Patent Publication No. Hei10-34281.
However, the above proposed apparatuses have another problem that casting is not always easy because of complex configurations of the required supply/discharge flow paths. Further, when the casing consists of a plurality of parts to be formed by casting separately, the supply/discharge flow paths should be connected during the assembly operation after casting, and thus the required assembly time is increased.